Mini Seismic Sensor
The Seismic Sensor (MSSH) detects the passage of people and vehicles from vibrations they cause in the ground. The vibrations are picked up by a geophone which activates an alarm. Ranges of the vibration sensor vary depending on ground and soil density. There are two versions of the Seismic Sensor (MSSH sensor only and MSID which includes the sensor and single channel transmitter).
This product can also be found here: